Friction material and method of forming the same

ABSTRACT

One exemplary aspect of the present disclosure relates to a method of forming a friction material. The method includes depositing a plurality of particles on a substrate such that the particles provide a plurality of projections and channels between adjacent projections. This disclosure also relates to the friction material itself, and a system including a mechanical component and the friction material.

RELATED APPLICATIONS

This application is a continuation of prior U.S. patent application Ser.No. 14/638,508, filed Mar. 4, 2015, the entirety of which is hereinincorporated by reference. The '508 Application claims the benefit ofU.S. Provisional Application No. 61/985,646, filed Apr. 29, 2014, theentirety of which is herein incorporated by reference.

BACKGROUND

Friction materials used in high torque applications need to withstandhigh temperatures. One example application is in the context ofsynchronizer rings, which are commonly found in manual and dual clutchtransmissions. Synchronizer rings are known to include an outer surfacehaving a plurality of gear teeth, and an inner surface having a frictionmaterial bonded thereto by way of an adhesive.

One known type of friction material includes machined (i.e., cut)grooves. These friction materials include a consistent density andsurface finish throughout. A second type of known friction material alsoincludes pressed or molded grooves and a consistent surface finishthroughout. However, unlike the first type, the material within thepressed/molded grooves has an increased density relative to theadjacent, raised material.

BRIEF DESCRIPTION OF THE DRAWINGS

A method of forming a friction material according to an exemplary aspectof the present disclosure includes, among other things, depositing aplurality of particles on a substrate such that the particles provide aplurality of projections and channels between adjacent projections.

A friction material according to an exemplary aspect of the presentdisclosure includes, among other things, a working layer provided by aplurality of particles. The working layer includes a first sectionhaving a first surface finish and a first density. The working layerfurther includes a second section having a second surface finishdifferent than the first surface finish and a second density differentthan the first density.

A system according to an exemplary aspect of the present disclosureincludes, among other things, a mechanical component, and a frictionmaterial connected to the mechanical component. The friction materialincludes a working layer provided by a plurality of particles. Theworking layer further includes a first section having a first surfacefinish and a first density, and a second section having a second surfacefinish different than the first surface finish and a second densitydifferent than the first density.

The embodiments, examples and alternatives of the preceding paragraphs,the claims, or the following description and drawings, including any oftheir various aspects or respective individual features, may be takenindependently or in any combination. Features described in connectionwith one embodiment are applicable to all embodiments, unless suchfeatures are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings can be briefly described as follows:

FIG. 1 illustrates an example mechanical component, which in thisexample is a synchronizer ring.

FIG. 2 is a flow chart illustrating an example method of making thedisclosed friction material.

FIG. 3 schematically illustrates a hopper assembly, which may be used inthe method of FIG. 2.

FIGS. 4A-4B are cross-sectional views of the example friction material,and illustrate the friction material at various stages of formation.

FIG. 5 is a close-up view of the encircled area in FIG. 1.

DETAILED DESCRIPTION

FIG. 1 illustrates an example mechanical component, which in theillustrated example is a synchronizer ring 10. While a synchronizer ring10 is illustrated, it should be understood that this disclosure extendsbeyond synchronizer rings. This disclosure is useful in otherapplications, such as other high torque applications, including, but notlimited to, clutch plates and torque converters.

The synchronizer ring 10 includes a plurality of gear teeth 12 extendingfrom a radially outer surface 14 thereof. During operation, a radiallyinner surface 16 of the synchronizer ring 10 is exposed to large amountsof heat. The radially inner surface 16 includes a friction material 18bonded thereto by way of an adhesive. The synchronizer ring 10 may bemade of steel or brass, as examples.

FIG. 2 illustrates an example method 20 for forming a friction material18 according to this disclosure. In the method 20, at step 22, aplurality of particles 24 (FIG. 3) are deposited onto a substrate 26.The particles 24 may be selected from any number of materials includingcarbon, silica, glass, and vermiculite. The substrate 26 may be a carbonfiber weave, paper, textile, aramid, or cloth material, to name a fewexamples. In one example, the particles 24 are deposited onto thesubstrate 26 via a hopper 28 and a spreader 30, which includes aplurality of elongate openings 32, as illustrated in FIG. 3. A spreader30 is not required in all examples.

The result of step 22 is illustrated in FIG. 4A. In FIG. 4A, thefriction material 18 includes the substrate 26 and a working layer 34,which is provided by the particles 24. The working layer 34 includes aplurality of projections 36 opposite the substrate 26. The projections36 are provided by the accumulation of particles caused by the elongateopenings 32 in the spreader 30.

After step 22, the projections 36 are naturally provided with a roundedcontour 38. Further, the projections 36 are spaced-apart by a distanceD₁. The distance D₁ can vary depending on the particular application(e.g., depending on the size of the synchronizer ring 10). In oneexample, the distance D₁ is within a range of 0.1875 to 0.5 inches. Inone specific example, D₁ is 0.375 inches.

The spaces between adjacent projections 36 define channels 40. At thechannels 40, the friction material 18 has a height D₂. The height D₂ maybe relatively small in some examples. In particular, in one example, thedistance D₂ may be such that the boundary of the channels 40 is providedby the substrate 26. On the other hand, the friction material 18 has aheight D₃ at the rounded contour 38 of the projections 36. The distanceD₃ is greater than the distance D₂.

After step 22, a resin R (schematically shown in FIG. 4A) is applied tothe friction material 18, at step 42. The particles 24 making up theworking layer 34 absorb the resin R. Step 42 may be repeated to ensurean appropriate level of saturation.

At step 44, the projections 36 are machined (e.g., sanded) toessentially flatten the previously rounded contours 38. The flattenedheight is shown at D₄. The height D₄ is less than D₃ and greater than D₂in one example. FIG. 4A shows, in phantom, the flat contour 46 of theprojections 36. FIG. 4B shows the machined projections 36 exhibiting theflat contour 46.

At step 48, the friction material 18 is applied to the mechanicalcomponent, which in this example is the synchronizer ring 10. In oneexample, which is schematically illustrated in FIG. 5, the frictionmaterial 18 is bonded to the radially inner surface 16 of thesynchronizer ring 10 by an adhesive layer 50. Heat H and pressure P areapplied to the friction material 18, the adhesive layer 50, and thesynchronizer ring 10 to ensure a proper bond. The adhesive layer 50 maybe any known type of adhesive suitable for high temperatureapplications. The adhesive layer 50 is provided between an outer surface51 of the friction material 18, which is opposite a radially innerworking surface 53 of the friction material 18.

The result of step 48 is shown in FIG. 5. In FIG. 5, the working layer34 is compressed such that the friction material 18 has a substantiallyuniform height D₅ throughout. The height D₅ in one example is less thanor equal to the height D₂.

When compressed, the working layer 34 has alternating first sections 52and second sections 54. In this example, the first sections 52correspond to locations where the projections 36 were provided(projections 36 are illustrated in phantom in FIG. 5). The secondsections 54, on the other hand, correspond to locations where thechannels 40 were provided (channels 40 are shown in phantom in FIG. 5).

Because of the machining from step 44, the first sections 52 have afirst surface finish which is smoother than the surface finish of thesecond sections 54. Since the second sections 54 are not machined instep 44, the second sections 54 are left with a rougher, more granularsurface finish (e.g., because of the unmachined nature of the depositedparticles 24).

Further, because the first sections 52 correspond to the locations wherethe projections 36 once existed, the first sections 52 are more densethan the second sections 54. The reasons for this increase in density istwofold. First, there were more particles forming the projections 36than in locations adjacent the channels 40. Thus, at step 42, more resinR was absorbed by the projections 36. Second, even after step 44, theflattened projections 36 had a height D₄ greater than the height D₂adjacent the channels 40. Thus, when compressed in step 48, theparticles within the first sections 52 are packed closer together thanthe particles in the second sections 54.

By providing the different first and second sections 52, 54, thefriction material 18 exhibits good wear characteristics because of therelatively smooth surface of the first sections 52 at the workingsurface 53. The friction material 18 also exhibits good frictionproperties because of the granular surface finish of the second sections54 at the working surface 53. The friction properties of the secondsections 54 are particularly beneficial for cold shifting, as thegranular nature of the second sections 54 helps to break the coolingfluid (e.g., oil) film adjacent the radially inner surface 16 of thesynchronizer ring 10.

Additionally, because the first section 52 has a higher density than thesecond sections 54, cooling fluid is directed to the second sections 54,and is allowed to permeate through the friction material 18 via therelatively lower density second sections 54, which increases the coolingof the synchronizer ring 10 and the friction material 18 itself. Thisincrease in cooling in turn increases performance of the synchronizerring, and extends the life of both the synchronizer ring and thefriction material.

In the example of FIG. 3, the openings 32 are linear openings, whichextend parallel to one another. This provides the friction material 18with a plurality of linear, parallel first and second sections 52, 54.Other patterns, such as zig-zags, come within the scope of thisdisclosure, however. While parallel first and second sections 52, 54 arementioned above, the first and second sections 52, 54 may not beparallel when applied to the radially inner surface 16 of thesynchronizer ring 10, as the radially inner surface 16 may be conical.

Although the different examples have the specific components shown inthe illustrations, embodiments of this disclosure are not limited tothose particular combinations. It is possible to use some of thecomponents or features from one of the examples in combination withfeatures or components from another one of the examples.

One of ordinary skill in this art would understand that theabove-described embodiments are exemplary and non-limiting. That is,modifications of this disclosure would come within the scope of theclaims. Accordingly, the following claims should be studied to determinetheir true scope and content.

What is claimed is:
 1. A method of forming a friction material,comprising: depositing a plurality of particles on a substantially flatsubstrate such that the particles provide a plurality of projections andchannels between adjacent projections, wherein the projections andchannels are formed by the particles as the particles are deposited onthe substrate, and wherein, as the particles are deposited, theprojections have a greater height than the channels and the channels aresubstantially parallel to one another.
 2. The method as recited in claim1, further comprising: applying resin to the deposited particles.
 3. Themethod as recited in claim 2, further comprising: machining theprojections such that the projections exhibit a flat contour.
 4. Themethod as recited in claim 3, further comprising: compressing theplurality of particles.
 5. The method as recited in claim 1, wherein theprojections and channels are formed entirely by the particles as theparticles are deposited on the substrate.